Derivatives of 5-oxo-1 beta-cyclopentane-heptanoic acid,5-ethylene acetals

ABSTRACT

RACEMIC OR OPTICALLY ACTIVE PROSTAGLANDIN E1 IS SYNTHESIZED FROM RACEMIC OR OPTICALLY ACTIVE PRECURSORS IN GOOD YIELD AT THE VARIOUS STEPS FROM 3A,6,7A-TETRAHYDRO4-METHYL-2-OXO-1B-INDANEHEPTANOIC ACID METHYL ESTER PROCEEDING THROUGH 2B-(2-CARBOXYETHYL)-3B-HYDROXY-5OXO-1B-CYCLOPENTANEHEPTANOIC ACID METHYL ESTER, $-LACTONE, 5-CYCLIC ETHYLENE ACETAL, 2A-(2-CARBOXY-2-FORMYLETHYL)3B-HYDROXY-5-OXO-1B-CYCLOPENTANEHEPTANOIC ACID METHYL ESTER, $-LACTONE, 5-CYCLIC ETHYLENE ACETAL, 2A-(2-CARBOXY2-OXOETHYL)-3B-HYDROXY-5-OXO-1B-CYCLOPENTANEHEPTANOIC ACID METHYL ESTER, $-LACTONE, 5-CYCLIC ETHYLEN ACETAL, ANND 3B-HYDROXY-2A-(3-OXO-1-OCTENYL)-5-OXO-1B-CYCLOPENTANEHEPTANOIC ACID METHYL ESTER, 5-CYCLIC ETHYLENE ACETAL.

"United States Patent O 8,833,612 DERIVATIVES F 0X0 IB-CYCLOPENTANE- HEPTANOIC ACID, S-ETHYLENE ACETALS Norman L. Wendler, Summit, David Taub, Metuchen, Harry L. Slates, Westfield, and Zbigniew S. Zelawski, Piscataway, N.J., assignors to Merck & Co., Inc., Rahway, NJ. No'Drawing. Filed Nov. 24, 1971, Ser. No. 201,979 Int. Cl. C07d 13/04 US. Cl. 260-3403 2 Claims ABSTRACT OF THE DISCLOSURE Racemic or optically active prostaglandin E is synthesized from racemic or optically active precursors in good yield at the various steps from 3a,6,7,7a-tetrahydro- 4-methyl-2-oxo 1,8 indaneheptanoic acid methyl ester proceeding through 25 (Z-carboxyethyl)-3B-hydroxy-5- oxo-lfl-cyclopentaneheptanoic acid methyl ester, fi-lactone, S-cyclic ethylene acetal, 2a-(2-carboxy-2-formylethyl) 3B-hydroxy-5-oxo-lfi-cyclopentaneheptanoic acid methyl ester, a-lactone, S-cyclic ethylene acetal, 2a-(2-carboxy 2-oxoethyl)-3B-hydroXy-5-oxo-lfi cyclopentaneheptanoic acid methyl ester, fi-lactone, S-cyclic ethylene acetal, and 3fl-hydroxy-2a-(3-oxo-loctenyl)-5-oxo-1,8 cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal.

BRIEF SUMMARY OF THE INVENTION This invention relates to a new and novel synthesis of prostaglandin E and more particularly to a synthesis which has a high degree of stereoselectivity at the points of generating the asymmetric centers of the molecule and produces either racemic or optically active prostaglandin E the activity corresponding to that of naturally occurring prostaglandin E. It relates further to a synthesis in which the yields are high in the several reaction steps. The invention relates still further to the novel compounds obtained as intermediates in the (i) and prostaglandin E synthesis and to the process for making such intermediates.

DETAILED DESCRIPTION OF THE INVENTION Prostaglandin E which may be depicted structurally O ll-OH on crmicoon Patented Sept. 3, 1974 duction of labor in pregnant females and for the termination of pregnancies by therapeutic abortion, M. P. Embrey. British Medical Journal, 1970, 2, 256-258: 258-260. Other uses, besides stimulation of smooth muscle, are described in the literature and include the lowering of blood pressure, effect on the mobilization of free fatty acids from adipose tissue, inhibition of lipolysis, and bronchodilating effects.

Heretofore, the supply of prostaglandin E as Well as of other prostaglandins, has been severely limited because only minute amounts of naturally occurring material are available, and partial biosynthesis by enzymes present in mammalian seminal vesicles has only atforded limited amounts of the products.

An object of this invention is to provide a stereoselective synthesis of (i) prostaglandin E, which compound has one-half the biological activity of the naturally occurring PGE and prostaglandin E which compound has of the biological activity of naturally occurring PGE and which may be used for the same biological effects as the natural compound.

A further object of the invention is to provide novel intermediate compounds some of which, in addition to being useful in the synthesis of (i) and PGE may themselves exhibit prostaglandin-like activity. An additional object is to provide a stereoselective total synthesis of the other members of the prostaglandin group which may be prepared by known methods from (i) and prostaglandin E Thus, for instance, (i) prostaglandin F may be obtained by reduction of PGE Other objects will become evident from the following description of the invention.

The novel process and intermediates of our invention are shown structurally in the following flow diagram, and immediately following this diagram the chemical names of the compounds are set forth.

(CH!) 5000 R1 H CH: O

(0H,)QCOORI (CHQOCOOR R2000 H Rzo Id: 1;

(CH2)6COOR1 (CHQCOORJ HOHC 0 0 O 1' 1* o it 0 0 O CH) COOR CH COOR as 1 0:0 (I 2h t OH (CHQ C OOH In the foregoing formulas R and R represent hydrogen, loweralkyl or aralkyl; R represents hydrogen or an acetyl group, and R and R represent hydrogen or acyl. The loweralkyl groups of this invention are those containing from 1 to 6 carbon atoms such as methyl, ethyl, propyl, and hexyl. The acyl groups of this invention are loweralkanoyl groups of from 2 to 6 carbon atoms such as acetyl, propionyl, butyryl, hexanoyl, and the like, and monocyclic aroyl groups such as benzoyl, toluoyl, and the like. The aralkyl groups are defined as loweralkyl groups substituted with an aromatic group of from 6 to 10 carbon atoms. Preferred are benzyl, xylyl and the like.

As a matter of convenience for understanding the foregoing fiowsheet and the following description of the invention, there follows a list of names of the chemical compounds 1-l0 inclusive.

1. (R =CH 3a,6,7,7a-tetrahydro-4methyl-2-oxo-15-indaneheptanoic acid methyl ester, 2-cyclic ethylene acetal.

2. (R =CH R =H) 3-acetyl-2a-(Z-carboxyethyl)-5- oxo-lfl-cyclopentaneheptanoic acid methyl ester, 5- cyclic ethylene acetal.

2. (R =R =CH;',) 3,3 acetyl-2u-[2 (methoxycarbonyl) ethyl]-5-oxo lfl cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal.

3. (R =R2=CHg, R =acetyl) 3,3 acetoxy 2o: [2-methoxycarbonyl) ethyl]-5-oxo-lfl-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal.

3. R =R =CH R =H) t-[Z-methoxycarbonylethyl]- 3fi-hydroxy-5-oxo-lB-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal.

4. (R =CH ZtZ-(Z carboxyethyl)-3p-hydroxy 5-oxocyclopentaneheptanoic acid methyl ester, -lactone, 5- cyclic ethylene acetal.

5. (R =CH 2a-(Z-carboxy-Z-formylethyl)-3fi-hydroxy- S-oxo-lfi-cyclopentaneheptanoic acid methyl ester, -lac tone, 5-cyclic ethylene acetal.

5A. la-(l-carboxy 2 oxoethyl)Jfi-hydrox-y-S-oxod/B- cyclopentaneheptanoic acid methyl ester, -lactone, 5- cyclic ethylene acetal.

6. (R =CH R =acetyl) 2a (2 acetoxy-Z-carboxyvinyl)-3; -hydroxy-5-oxo -"lfi-- cyclopentaneheptanoic acid methyl ester, -lactone, 5-cyclic ethylene acetal.

7. (R zCH 2a-formyl3;3-[(methoxalyl)oxy]-5'- oxo- I[:l-cyclopentaneheptanoic acid methyl ester, 5 -cyclic ethylene acetal. v V} 7A. (R =CH 3;? [(methoxalyl)oxy] 2a (-3-oxo-loctenyl)-5-oxo-l[i-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetalu 8. (R :CH R =H) 3 .3-hydroxy-2a-(3-oxo-l-octenyl)- 5-oxo-lfl-cyclopentanchcptanoic acid methyl ester, 5- cyclic ethylene acetal.

9. (R :CH R :H) Prostaglandin E methyl ester, cyclic ethylene acetal.

9. (R =R =H) Prostaglandin E cyclic ethylene acetal.

l0. Prostaglandin E I In the foregoing list of names and in subsequent discussions, the esters and acyl groups have been referred to as methyl esters and acetyl groups respectively because the detailed examples refer to such groups; but itis to be understood that other esters are within the scopeof the invention as shown by the symbols R R R and- R in the flow diagram.

The synthesis of prostaglandin E in-its racemic- (1-) or natural form starts .with 3a,'6;7,7a-tetrahydro-'4 methyl-Z-oxo-lB-indaneheptanoic acid methyl ester l, R =CH in its racemic or optically ,active form. The preparation of the racemic and opticallyactive forms of compound 1 are disclosed in US. Patent Application Ser. No. 201,959 filed on Nov. 24,1971.

In the first step of this synthesis either-racemlc or optically active 3a,6,7,7a-tetrahydroA-methyl-2 oxo-lfiindaneheptanoic acid methyl ester (l, 'R =CH is converted to 3a,6,7,7a tetrahydro --4 --'methyl-2-oxo lfi-in'- danehcptanoic acid methyl ester; cyclic ethylene acetal by reaction with ethylene glycolin the presence of an acid such as p-toluenesulfonic' acid.'-The resulting'acetal is then oxidized with an oxidizing agent such as potassium permanganate preferably'in the presence of sodium periodate, to produce 3-acetyl-2m (2-carboxyethyl) 5 oxolB-cyclopentaneheptanoic acid methyl ester, S-cyclicethylene acetal (2, R =CH R =H). It is preferred to include potassium carbonate in the reactionsyster'rrwhich facilitates the oxidation as well as partially epimerizing the 3-carbon atom such that the wacetyl group becomes a S-acetyl group. The reaction product-is a mixture of 3a.- acetyl and 3B-acetyl-2a-(2-carboxethyl)-5-oxo-Iii-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal (2, R =CH R=H).

The epimeric mixture is then treated with an excess of a diazoloweralkane or diazoaralkan'e to prepare the ester derivative which is then epimerized, forming the 3t9-acetyl group from the 3ix-acetyl group, with an alkali metal loweralkoxide, preferably the same alkoxide group present on the ester functions in order to prevent transesterification. In order to accomplish thi the epimeric mixture is dissolved in a loweralkanol and treated with a loweralkanol solution of the alkali metal alkoxide at from 10 to 50 C., preferably room temperature, for from 10 to 30 hours, affording all 3B acetyl-2a-2-[me; thoxycarbonylethyl]-5-oxo- 1fl-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal (2, Ri=R =CH with no traces of the Biz-acetyl derivative. v

Compound 2-(R :R CH is then oxidizedwith an oxidizing agent as such as an organic peracid, preferably trilluoro peracetic acid, m-chloroperbenzoic acid and the like, affording 3/3-acetoxy-2u-[2-methoxycarbonylethyl]- S-oxo-lfl cyclopentaneheptanoic acid methyl ester, 5-cy clic ethylene acetal (3, R =R =CH R zacetyl). The reaction mixture is generally buffered with a weakly alka line buffering agent such as sodium-monohydro gen phosphate. The reaction is run generally at room temperature forfrom 10 to 30 hours. Thin layer chromatography of an aliquot portion indicates the degree of completion of the reaction and additional oxidizing agent may be added if necessary until the reaction is complete.

Compound 3-(R =R :CH R zacetyl) is treated with an alkali metal alkoxide in the corresponding loweralkanol. The reaction is run for from 1 to 4 hours at about room temperature and worked up by techniques known to those skilled in the art affording Za-[Z-methoxycarbonylethyl]-3,9-hydroxy-5 oxo-lficyclopentaneheptan'oic acid methyl ester, S-cyclic ethylene acetal (3, R =R =CH R =H). The hydroxy compound is then lactonized with an alkali metal alkoxide preferably potassium t-butoxide in an inert solvent such as benzene, toluene, and the like at the reflux temperature of the solvent employed. The solvent is preferably one which codistills with the loweralkanol corresponding to R Distillation of the solvent is continued until a thin layer chromatogram of an aliquot indicates conversion to lactone 4 is complete. This normally requires from 1 to 6 hours of distillation. There is recovered 2a-(2-carboxyethyl)-3fi-hydroxy S-oxo-lfl-cyclopentaneheptanoic acid methyl ester, fi-lactone, S-cyclic ethylene acetal (4, R =CH The next step in the racemic or optically active synthesis is the formylation of compound 4 with a loweralkyl formate in the presence of an alkali metal hydride at from to 40 C. for from 95 to 6 hours. The exothermal nature of the reaction usually necessitates adding the alkali metal hydride portionwise and maintaining the temperature at from 0 to 10 during the first hour of the reaction. The product is 2a-(2-carboxy-2-formylethyl)- 3fl-hydroxy-5-oxo-lp-cyclopentane heptanoic acid methyl ester, tS-lactone, S-cyclic ethylene acetal sodium salt, which on treatment with a mild acid such as sodium dihydrogen phosphate in aqueous solution liberates compound -(R =CH The formyl derivative is ozonized in the presence of an organic base such as pyridine at temperatures substantially below 0 C., preferably Dry Ice temperatures, by bubbling ozone or a mixture of O and 0 into the reaction mixture until an excess is present, indicated by the presence of a pale blue color. The resulting 2a-(2-carboxy- 2-oxoethyl) 3fl-hydroXy-5-ox0-lfl-cyclopentaneheptanoic acid methyl ester, 6-lactone, S-cyclic ethylene acetal (5A, R =CH which is isolated but not purified is reacted with an acylating agent in the presence of an organic base. Preferred are acetylating agents as acetic anhydride, acetyl chloride, and the like, however, other acylating agents such as benzoyl chloride may be utilized. The reaction is worked up by techniques known to those skilled in the art yielding 2a-(Z-acetoxy-Z-carboxyvinyl)-3p-hydroxy-S-oxo-lp-cyclopentaneheptanoic acid methyl ester- 6 lactone, 5 cyclic ethylene acetal (6, R =CH R =acetyl).

In the next step the above acyl compound is oxidized with osmium tetroxide in the presence of an alkali metal periodate in methanol. The compound is treated first with the osmium tetroxide until the solution darkens. The alkali metal periodate, preferably sodium periodate is then added portionwise over from 2 to 6 hours and the reaction stirred at about room temperature for from 2 to 6 hours, aflording 2a-formyl 3,8 [(methoxalyDoxyJ-S-oxo-lficyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal (7, R =CH A Wittig reaction is employed to form the octenone side chain at the 2-position of the cyclopentane ring. The formyl compound (7, R =CH is treated with an alkali metal hydride and dimethyl 2-oxoheptylphosphonate in an anhydrous, inert solvent, such as tetrahydrofuran, dioxane, and the like. The intermediate 3,3-[(methoxalyl) oxy]-2u-(3-0xo-1-octenyl) 5 oxo 1 3 cyclopentaneheptanoic methyl ester, 5-cyclic ethylene acetal (7A, R =CH is treated with a 1,2-diamine such as ethylene diamine at from 10 to 25 C. for from 15 minutes to 2 hours cleaving the 3fl-methoxalyl-oxy group and affording Sit-hydroxy 2a (3-oxo-1-octenyl)-5-oxo-1B-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal (8, R =CH R =H).

The side chain keto group is reduced to a hydroxyl group with a mild reducing agent such as an alkali metal borohydride. The reduction is complete in from 15 min utes to 2 hours at from -20 to 25 C. The reaction affords a mixture of the R and S stereoisomers because both 5- and a-hydroxy groups are formed, of which the a-hYdIOXY is preferred. The reaction mixture is chromatographed whereupon the isomers are separated and pure prostaglandin E methyl ester-S-cyclic ethylene acetal [3fl-hydroxy-2a-(3a[S]-hydroxy-1-octenyl) 5 oxo-lflcyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal, (9, R =CH R =H)] is obtained. The 3 3[R]- hydroxy compound is separately obtained from the chromatographic column, and back oxidized by treatment with manganese dioxide to afford the keto starting material (8, R =CH R =H) which can be recycled.

It is advantageous to employ the O-acyl, preferably the acetyl derivative of the Ftp-hydroxyl group of compound 8 during the reduction and back oxidation of the side chain keto group. The acyl group has no deleterious effects on the reduction to the hydroxyl group. However, yields are considerably improved during the back-oxidation of the [R] hydroxyl group with manganese dioxide if the acyl group is present.

The final steps in this synthesis of racemic or optically active PGE involves the removal of the protecting groups. The esters are hydrolyzed to the free acid using basecatalyzed hydrolysis in aqueous media. Preferred catalysts are alkali metal hydroxides such as potassium hydroxide in aqueous solution at from 0 to 40 C. for from 1 to 5 hours. The thus produced prostaglandin E -5-cyclic ethylene acetal (9, R =H, R =H) is treated with an aqueous acid preferably an organic acid such as acetic acid, at about room temperature for from 1 to 5 hours, cleaving the cyclic acetal and yielding prostaglandin E Depending on whether the starting material (compound 1) is racemic or optically active, racemic or optically active PGE, will be obtained. No loss in optical activity is observed when optically active (1) is employed; the reaction sequence 1) thru (10) being stereoselective and not tending to the racemization of any of the intermediates.

There are two series of optically active intermediates, one leading to PGE and the other to PGE The former is the naturally occurring form of PGE and the one which possesses all of the biological activity. Both series of intermediates can be prepared using the procedures of the following examples. The series of intermediates leading to the naturally occurring PGE is preferred and when referred to hereinbelow are termed of the natural series.

The following examples are presented in order that the invention might be more readily understood. They should not be construed as being limitative of the invention.

EXAMPLE 1 311,6,7,7a-tetrahydro-4-methyl-2-oxo-lfl-indaneheptanoic acid methyl ester, 2-cyclic ethylene acetal A mixture of 11.8 g. of *:)-3a,6,7,7a-tetrahydro-4 methyl-Z-oxo-lfl-indaneheptanoic acid methyl ester, 27 ml. of ethylene glycol and 300 mg. of p-toluene sulfonic acid mono-hydrate in 600 ml. of benzene is refluxed with stirring for 18 hours using a Dean-Stark trap to separate the water formed in the reaction. The reaction mixture is cooled and added to 300 ml. of cold 5% potassium bicarbonate. The layers are separated and the aqueous layer extracted twice with 2:1 benzene-hexene. The combined organic fractions are washed 3 times with saturated aqueous sodium chloride, dried over sodium sulfate and evaporated to dryness affording 12.6 g. of +-)-3a,6,7,7a-tetrahydro- 7 4-methyl-2-oxo-lfi-indaneheptanoic acid methyl ester, 2- cyclic ethylene acetal, NMR (C D 6 3.56 [4H-ethylene group].

When in the above procedure +)-3a,6,7,7a-tetrahydro- 4-methyl 2 oxo-1fl-indaneheptanoic acid methyl ester [a] -|1l.6 is employed in place of the racemic mixture there is obtained optically active -3u,6,7,7a-tetrahydro-4-methyl 2 oxo-lfi-indaneheptanoic acid methyl ester, 2-cyclic acetal [a] =26.

EXAMPLE 2 35 Acetyl-2a-(Z-methoxycarbonylethyl)-5-oxo-lB-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal A. 3 Acetyl-2a- (2-carboxyethyl)-5-oxo-l;3-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal.- To a stirred solution of 5.69 g. of (i)-3z,6,7,7a-tt1"3hy dro-4-methyl-2-oxo-lB-indaneheptanoic acid methyl ester, 2-cyclic ethylene acetal in 410 ml. of t-butanol and 11 ml. of water is added a mixture of 5.80 g. of potassium carbonate, 22.8 g. of sodium periodate, and 270 mg. of potassium permanganate in 1230 ml. of water. The reaction mixture is stirred at 20-25 C. for 20 hours and concentrated in vacuo to remove the t-butanol. Ethylene glycol (0.5 ml.) is added and the reaction mixture extracted with 1: l ether-benzene to remove neutral material. The aqueous layer is acidified with solid sodium dihydrogen phosphate and extracted 4 times with 1:1 ethyl acetate-benzene. The organic layer is dried over sodium sulfate and evaporated to dryness in vacuo affording (i)-3-acetyl-2a-('2-carboxyethyl)-5-oxo-lfl-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal as a mixture of the 3m and 3p isomers.

B. 318 Acetyl-2a-(Z-methoxycarbonylethyl)-5-oxo-1flcyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal.-The above (1-)-3-acetyl-2a-(2-carboxyethyl)-5- oxo-lp-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal is dissolved in ml. of ether and treated with ethereal diazomethane until an excess is present as indicated by a persistent yellow color. After 5 minutes the reaction mixture is evaporatcd to dryness in vacuo and the residue dissolved in ml. of methanol and 2 ml. of 1N sodium methoxide in methanol is added. The reaction mixture is stirred for 18 hours at room temperature and added to cold saturated aqueous sodium dihydrogen phosphate. The methanol is removed in vacuo and the mixture extracted with 1:1 ethyl acetate-benzene. The organic extract is dried over sodium sulfate and evaporated to dryness affording i)-3fl-acetyl-2a-(Z-methoxycarbonylethyl)-5-oxo-lfl-cyclopentaneheptanoic acid methyl ester, 5- cyclic ethylene acetal, NMR (CDCl;.;) 6 2.13

When in the above procedures ()-3a,6,7,7-tetrahydro-4-methyl-2-oxo-lfi-indaneheptanoic acid methyl ester, 2-cyclic ethylene acetal is employed in place of the racemic compound there is obtained 3B-acetyl-2oz-(2-methoxycarbonylethyl)-5-oxo-1 p-eyclopentaneheptanoic acid, methyl ester, S-cyclic ethylene acetal, [a] q-|-6.8.

EXAMPLE 3 3B Acetoxy 2o: (2-methoxycarbonylethyl)-5-oxo-1B- cyclopentaneheptanoic acid methylester, 5-cyclic ethyl ene acetal 60 g. of solid disodium monohydrogen phosphate is added to a stirred solution of 4.50 g. of (:)-3;9-acetyl-2tz- (Z-mthoxycarbonylethyl) 5 oxo-lp-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal in ml. of methylene chloride and the mixture cooled to 0 C. 45 ml. of freshly prepared 0.3M trifiuoroperacetic acid in methylene chloride is added and the reaction mixture stirred for 18 hours at room temperature. A thin layer chromatogram of an aliquot portion of the reaction mixture indicates the reaction to be about 60% complete. An additional 40 ml. of the 0.3M trifiuoroperacetic acid in 8 methylene chloride is added. After stirring an additional 24 hours the reaction iscomplete. The reaction is filtered, the precipitate washed with methylene chloridea'nd the, combined filtrates washed with coldaqueous potassium iodide and cold aqueous sodium thiosulfate toremove residual peracid. Theorganic extract is Washed with water, dilute aqueous potassium bicarbonate and saturated aqueous sodium chloride. The organic layer is dried over sodium sulfate and evaporated to dryness in vacuo affording (i) 3,9 acetoxy 2w.(Z-methoxycarbonylethyl)-5- oxo-lfi-cyclopentaneheptanoic acid .methyl ester, S-cyclic ethylene acetal as a colorless oil, NMR (CDCl;;) 6 2.01 [3HCH COO].

When in the above procedure (+)-3fi-acetyl-2a-( 2 methoxycarbonylethyl) 5-oxo-1fi-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethyleneacetal is employed in place of the racemic mixturethere is obtained optically active 35-acetoxy-2m-(2-methoxycarbonylethyl)-5-oxo-lp3- cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal, of the natural series.

EXAMPLE 4 2a (2 Carboxyethyl)-3,8-hydroxy-5-oxo-lfi cyclopentaneheptanoic acid methyl ester, fi lactone, 5-cyclic eth-' ylene acetal A. 2a-(Z-methoxycarbonylethyl)-3flhydr0xy-5-0xo 1p cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal.6 ml. of 1.00N sodium methoxide is addedto a stirred solution of 4.25 g. of (i)-3fi-acetoxy-2zz-(2-me-. thoxycarbonylethyl)-5-oxo-1 fl-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal in-25 ml.- of methanol under a nitrogen atmosphere and stirred at'room temperature for 2 hours. The reaction mixture is poured into excess cold saturated aqueous sodium dihydrogen phos phate and extracted with 1:1 ethyl acetate-benzene. The organic extract is dried over sodium sulfate and evapo-. rated to dryness in vacuo. The residue is purified chromatigraphically employing 180 g. of silica gel and 'eluting with 25% acetone in chloroform affording pure "(i-)-2a- (Z-methoxycarbonylethyl) 318 --hydroxy-5-oxo-l5-cyclo pentaneheptanoic acid methylester, .5-cyclic ethylene acetal. I

When in the above procedure optically active-3fl-ace toxy-2a-(Z-methoxycarbonyltethyl) 5 oxo-lfi-cyclopem taneheptanoic acid methyl ester, 5-cyclic ethylene acetal of the natural series is employed in'place of the racemic mixture there is obtained (+)-2a-(2methoxycarbonyl ethyl)-3fi-hydroxy 5 *oxo-lfi-cyclopentaneheptanoic 'acid' methyl ester, S-cyclic ethylene acetal [a] +l4.7'.*

B. 2a-(2-carboxyethyl)-35-hydroxy 5' oxo-lfi-cyclm pentaneheptanoic acid methyl ester tS-lacton e, 5-cyc lic eth ylene acetal.-l.66 g. of (i)-2u-(2-methoxycarbonylethyl)-3/3-hydroxy 5 oxo-lfi-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal is dissolved in 350 ml. of benzene in a nitrogen atmosphere and rendered anhydrous by removing 30 ml. of benzene by distillation; 0.25 ml. of 0.66M potassium t-butoxide in t-bu tanol is added and an additional ml. of benzene'rem'oved by distillation over a period of 4 hours. The reaction mixture is cooled, added to cold saturated aqueous -sodium dihydrogen phosphate, and extractedwith benzene; The combined organic layers are washed with saturated aqueous sodium chloride, dried over sodium sulfate, and evaporated to dryness in vacuo affording -)-2a-(2-carboxy-" ethyl)-3fi-hydroxy 5-oxo-lfi-cyclopentaneheptanoic acid methyl ester, fi-lactone, 5-cyclic ethylene acetal as a pale yellow oil.

When in the above procedure (+)-2a-(2-methoxycar bonylethyl)-3[3-hydroxy 5 oxo-lfi-cyclopentanehepta noic acid methyl ester, 5-cyclic ethylene acetal is em ployed in place of the racemic mixture there is obtained optically active Za-(Z-carboxyethyl)-3fi-hydroxy-5-oxoll3-cyclopentaneheptanoic acid methyl ester, fi-lactone, 5-cyclic ethylene acetal of the natural series.

9 EXAMPLE 5 2a-(2-carboxy 2 formylethyl)-3B-hydroxy-5-oxo-lB-cyclopentaneheptanoic acid methyl ester, li-lactone, S-cyclic ethylene acetal 210 mg. of 50% sodium hydride dispersion is added to a stirred solution of 1.36 g. of (:)-2a-(2-carboxyethyl)- 3B-hydroxy 5 oxo-lfl-cyclopentaneheptanoic acid methyl ester, fi-lactone, 5-cyclic ethylene acetal in 25 ml. of methyl formate under a nitrogen atmosphere over a period of 3 minutes at C. The reaction mixture is stirred for 1 hour at 0 C. and 4 hours at 20 C. The solvent is removed in vacuo and the residue triturated with ether and the precipitate filtered and washed with ether. The precipitate is dissolved in cold saturated aqueous sodium dihydrogen phosphate, extracted with ethyl acetate, dried over sodium sulfate and evaporated to dryness. The residue is crystallized from ether-hexane affording (1)21- (2-carboxy-2-formylethyl)-3p-hydroxy oxo 1B cy-- clopentaneheptanoic acid methyl ester, -lactone, S-cyclic ethylene acetal, m.p. 88-90 C.

When in the above procedure optically active-2a-(2 c'arboxyethyl)-3B-hydroxy 5 oxo-lB-cyclopentaneheptanoic acid methyl ester, 6-lactone, 5-cyclic ethylene ace ml of the natural series is employed in place of the racemic mixture, there is obtained optically active 2a-(2-car boxy2-formylethyl)-313 hydr0xy-5 oxo 1p cyclopen tarieh e'ptanoic acid methyl ester, 6-lactone, S-cyclic ethylene acetahof the natural series, m.p. 80-81.

EXAMPLE 6 2a-(2-acetoxy 2 carboxyvinyl)-3B-hydroxy-5-oxo-1B- cyclopentaneheptanoic acid methyl ester, a-lactone, Scyclic ethylene acetal A. 2a-(2-carboxy. 2 oxoethyl)-3B-hydroxy-5-oxo- IB-cyclopentaneheptanoic acid methyl ester, a-lactone, 5-cyclic ethylene acetal.-A solution of 460 mg. of (i)- 2a-(2-carb0xy 2 formylethyl)-3B-hydroxy-5-oxo-1B-cyclopentaneheptanoicacid methyl ester, fi-lactone, S-cyclic ethylene acetal in 6 ml. of methylene chloride and 4.4 ml. of pyridine is cooled to 70 C. and treated with a 5% ozone-oxygen mixture until an .excess of ozone is present as indicated by a persistent pale blue color. The excess ozone is evaporated by bubbling nitrogen into the reaction and the solvents are removed in vacuo. The residue is triturated with ether affording crystalline -)-2a-(2- carboxy 2 oxoethyl)-3fi-hydroxy 5 oxo-lfl-cyclopentane heptanoic acid methyl ester, 6-lactone, S-cyclic ethylene acetal, m.p. 1 14-1 16 C.

B. 2a-(2-acetoxy 2 carboxyvinyl) 3/3 hydroxy-S- oxo-lfi-cyclopentaneheptanoic acid methyl ester, 6-lactone, S-cyclic ethylene acetal.The ozonolysis product is acetylated in 6 ml. of pyridine and 3 ml. of acetic anhydride at room temperature for 17 hours. 6 ml. of xylene is added and the reaction mixture evaporated to dryness in vacuo. The residue is triturated with ether-hexane affording crystalline (i)-2tz-(Z-acetoxy-2-carboxyvinyl)- 3fi-hydroxy-5-oxo-lB-cyclopentaneheptanoic acid methyl ester, 6-lactone, S-cyclic ethylene acetal, mp. 82-84 C.

When in the above procedure optically active-2a-(2- carboxy 2 formylethyl)-3B-hydroxy-5-oxo-lfi-cyclopentaneheptanoic acid methyl ester, fi-lactone, S-cyclic ethylene acetal is employed in place of the racemic mixture, there is obtained (+)-2a(2-acetoxy-2-carboxyvinyl)-3/3- hydroxy 5 oxo-lfl-cyclopentaneheptanoic acid methyl ester, fi-lactone, S-cyclic ethylene acetal [oz] {-30 of the natural series.

EXAMPLE 7 2a-formyl-3fl-[(methoxalyl)oxy] 5 oxo 1 3 cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal 14 mg. of osmium tetroxide in 1.4 ml. of methanol is added to a stirred solution of 430 mg. of (i)-2a(Z-E1C8- toxy 2 carboxyvinyl) 3B hydroxy-S-oxo-lB-cyclopentaneheptanoic acid methyl ester, Zi-lactone, 5-cyclic ethylene acetal in 16 ml. of methanol. The reaction mixture darkens in 1015 minutes and 440 mg. of powdered sodium periodate is added portionwise over 3 hours. The reaction mixture is stirred for 1 additional hour, filtered, and the filtrate evaporated to drynes in vacuo. The residue is dissolved in 2.5 ml. of 1:1 ethyl acetate-benzene and the solution washed with water and saturated aqueous sodium chloride. The organic layer is dried over sodium sulfate and evaporated to dryness in vacuo affording (i)- 2a-formyl-3 8-[(methoxalyl)oxy] 5 oxo-lficyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal as an oil.

When in the above procedure (+)-2a-(221CBIOXY-Z-CHI- boxyvinyl 3B hydroxy-S-oxo-lfi-cyclopentaneheptanoic acid methyl ester, 5-lactone, 5-cyclic ethylene acetal is employed in place of the racemic mixture, there is obtained optically active 2a formyl 3t! [(methoxalyl) oxy] 5 oxo lfl-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal, of the natural series.

EXAMPLE 8 35-Hydroxy 2oz (3-oxo-l-octenyl)-5-oxo 113 cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal A. 3fi-[(methoxalyl)oxy] 2a (3-oxo l octenyl)- 5-oxo 1,8 cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal.230 mg. of dimethyl-2-oxoheptyl phosphonate in 4 ml. of tetrahydrofuran is added to a stirred suspension of 50 mg. of 50% sodium hydride dispersion in 10 ml. of tetrahydrofuran under a nitrogen atmosphere at 0 C. The reaction mixture is stirred at --0 C. for 30 minutes and a solution of 420 mg. of i )-Zaformyl 3 B [(methoxalyl)oxy] 5 oxo-lfi-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal in 4 ml. of tetrahydrofuran is added dropwise over 5 minutes. After 10 minutes the mixture is allowed to warm to room temperature and stirred for 2 hours. The reaction is cooled to 10 C., added to cold saturated aqueous sodium dihydrogen phosphate and extracted with ethyl acetate. The organic extract is washed with saturated aqueous sodium chloride, stirred over sodium sulfate, and evaporated to dryness in vacuo affording ')-3B-[(methoxalyl)oxy]- 2a-(3-0X0 1 octenyl)-5oxo-lB-cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal containing a smaller amount of (i)-3B-hydroxy 20: (3 oxo-loctenyl)-S-oxo 1,8 cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal.

B. Bfl-Hydroxy 2a (3-oxo-l-octenyl) 5 oxo-lflcyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal.The above mixture is dissolved in 7.5 ml. of methanol and 60 mg. of ethylenediamine in 5 ml. of methanol added dropwise at 0 C. The reaction mixture is stirred for 45 minutes at 20 C. and the solvent remover in vacuo. The residue is partitioned between ethyl acetate and saturated aqueous sodium dihydrogen phosphate. The layers are separated and the aqueous layer extracted with ethyl acetate. The combined extracts are dried and evaporated to dryness in vacuo. The residue is chromatographed on 35 g. of silica gel eluting with 30% acetone and chloroform taking 40 fractions of 4 ml. each. Fractions 5-14 are combined and evaporated to dryness in vacuo affording 250 mg. of pure (i)-3B-hydroxy-2u- (3-oXo-1-octenyl) 5 oxo lfi cyclopentaneheptanoic acid methyl ester, 5-cyclic ethylene acetal, t max. (methanol=232 nm. (E 12,500).

When in the above procedure, optically active 3/3- [(methoxalyl)oxy] 5 oxo 113 cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal of the natural series is employed in place of the racemic mixture, there is obtained optically active-(3fl-hydroxy 2a (3-oxo-loctenyl) 5 oxo-lB-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal.

r EXAMPLE 9 Prostaglandin E methyl ester, cyclic ethylene acetal.

[3,8-hydroxy 2a (3 [S} hydroxy 1 octenyl)-5- oxo 1,8 cyclopentaneheptanoic acid methyl ester, 5- cyclic ethylene acetal] 23 mg. of sodium borohydride in 2 ml. of methanol at C. is added dropwise to a stirred solution of 245 mg. of (:)-3fi-hydroxy 2a (3-oxo l octenyl)-S-oxolfi-cyclopentaneheptanoic acid methyl ester. S-cyclic ethylene acetal in 6 ml. of methanol at l0 C. The reaction mixture is stirred for 40 minutes at l(l C. and added to 50 ml. of saturated sodium dihydrogen phosphate and extracted with ethyl acetate. The extracts are washed with saturated aqueous sodium chloride, dried over sodium sulfate, and evaporated to dryness in menu. The residue is chromatographed on 20 g. of silica gel eluting with 50% acetone-chloroform and collecting 50 fractions of 8 ml. each. Fractions 8l8 are combined and evaporated to dryness affording (i)-3fl-hydroxy-2a-(3[R]hydroxyl-octenyl) 5 0x0 1,3 cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal. The 3;3[R]isomer (100 mg.) is dissolved in 5 ml. of ethyl acetate and stirred with 2 g. of activated manganese dioxide for 6 hours. The mixture is filtered, the precipitate washed with acetone and the combined filtrates and washings evaporated to dryness in vacuo affording recyclicable (i)-3}3-hydroxy 2a(3-oxo-1-octenyl)-5-oxo 1;: cyclopentaneheptanoic acid methyl ester, 5 -cyclic ethylene acetal.

Fractions 21-25 are combined and evaporated to dryness affording (:)-3,8-hydroxy 2a (3[S] hydroxy-loctenyl)-S-oxo cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal m.p. 54-5 6 C.

When in the above procedure optically active 3 8- hydroxy-2a-(3-oxo 1 octenyl)-5-oxo l5-cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal is employed in place of the racemic mixture, there is obtained optically active prostaglandin E methyl ester, cyclic ethylene acetal, [3;8-hydroxy 2a (3[S]-hydroxyl-octenyl) 5 oxo 15 cyclopentaneheptanoic acid methyl ester, S-cyclic ethylene acetal] of the natural series, m.p. 48-51 C.

EXAMPLE 1O Prostaglandin E cyclic ethylene acetal. [3,8 hydroxy-2a- (3[S]hydroxy-l-octenyl) 5 oxo-1fi-oxocyclopentaneheptanoic acid, 5-cyclic ethylene acetal] A solution of 45 mg. of potassium hydroxide in 2.5 ml. of water at 0 C. is added dropwise to a solution of 40 mg. of (:)-3fl-hydroxy 2a (3[S]hydroxy-l-octeny1)- 5-oxo lfi cyclopentaneheptanoic acid methyl ester, 5- cyclic ethylene acetal in 1 ml. of methanol at 0 C. in a nitrogen atmosphere. The reaction mixture is allowed to 12 warm to room temperature and ir'red for 3 hours. Cold dilute'aqueous potassium bicarbonate is addedfiofihefre'i action mixture" and-the mixture extracted --'with hexane. Solid sodium dihydrogen phosphate is-a'dded to'the aimeous layer and the latter is .extractedwth lzl e1hyl, acetatebenzene. The organic layer'is dried o ver sqdium' sulfate and evaporated to dryness iII- ViHQIt O alfordin g i )-pros taglandin E S-cyclic ethylene acetal i -3 -hydroxy;. 2a-(3[S]-hydroxy 5 1 octenyl) 5 oxo l B.:-p} (Qcyl peutaneheptanoic acid, Li-cyclic. ethylene=acetal1 84 C. r 1 V, When in the above procedure optically active droxy 2a (3[S]hydroxy 1 -..oct e nyl);5,-oxo gyclo; pentaneheptanoic acid methyl ester 5 cyclic-ethylene acetal of the naturaliseries isemployed in place qffth racemic mixture there isob tained optically a iit iv e prostaglandin E S-cyclic ethylene acetal ofrthe na turalserjes m.p. 8183 c. J

EXAMPLE ll ,I C

Prostaglandin'fi I A mixture of 37 mg of (i)pro stagla ndin e 's'fycnc. ethylene acetal and 3 nfl. of '1 i 1 acetic"acid i stirred at 25 C. for 3 hours. Saturated q hydrogen phosphate solution' is added andt act' onmiio ture extracted with 1:1 ethyl aceta'tebeni ."fhe rgann; layer is washed with saturated aqiieou's sod dried over sodium sulfatef'and evaporated to. dry 1 1110110 affording a crystalline residue iivhich is fecry s'tal lized from ethyl acetate-benzene affording (i)-prostaglandin E mp 111-113? C. When in the above pro cedure bpti lly ac glandin E cyclic ethylendatal offtifei f (1" employed in place of the racer nic mixtti'refthre is 'obtained ()-prostaglandin E mip. lI2 -}1'3-C:-[bz] 58. i i: *1?

What is claimed is: J 1. The loweralkyl, benzyl'and-xylyl-esters-0P3}? lhyi droxy 2a (3[S]-hydroxy-'-'-1 'czcteniU -mb-lfi-qqld; pentaneheptanoic acid,-5-cyclie ethylene acetahand-sterebm isomers thereof. .v 2. The compound of Claim: lain zwhich'the .loweralkyl ester is the methyl ester. 1" :1 1' l ReferencesCited v Taub, et al., ChemicalCoinmurifcations ffingf' 1970, pp. 1258-9. H I

DONALD G. DAUS, Primary Examiner J. H. TURNIPSEED, AssistantExaipiner JS- ZP Q I -TTJ 260-468 R, 468 D, 485 L, 514 D; 4241 4105. 

